How to use
Pick your date of birth and everything updates instantly: your exact age broken down into years, months, and days; the total number of days you've been alive; and how many days are left until your next birthday, with the date and weekday. It works just as well for other people and things: a parent checking a child's age in months and days for a pediatric form, figuring out exactly how old a grandparent is turning, or counting how many days old a puppy or a sourdough starter is. Use the "Copy result link" button to save or share a result; the birthday travels in the link itself, not through any server.
How the age is calculated
This calculator counts age the way official documents do: by the calendar, not by dividing days by 365:
- Years: each completed birthday adds one year. You're 25 until the moment your 26th birthday arrives, no matter the month.
- Months: whole calendar months completed since your last birthday.
- Days: whatever days are left over after the whole years and months are counted.
- Total days alive = calendar days between your birth date and today, leap days included.
- Space traveled = days alive × 86,400 seconds × Earth's mean orbital speed of 29.78 km/s (NASA Earth fact sheet); light travels 299,792.458 km/s.
- Moon distance = the distance series in Meeus ch. 47 (table 47.A), within 10 km of NASA JPL Horizons from 1950 to 2100; rounded to the nearest 100 miles and 100 km.
- Next birthday = the next occurrence of your birth month and day, counted from today. Born on February 29? In non-leap years it's counted as March 1.
Because months are 28 to 31 days long, the months-and-days part depends on which end you anchor. Like most age calculators, this one anchors on the birthday side: years and months are filled first, and the remainder becomes days.
Examples
Someone born on January 1, 2000 is, as of July 22, 2026, exactly 26 years, 6 months, and 21 days old: the 26th birthday passed on January 1, 2026, six full months bring the anchor to July 1, and July 1 to July 22 leaves 21 days. Their total days alive is 9,699 days, and the next birthday (January 1, 2027) is 163 days away. A baby born on March 15, 2026 is 4 months and 7 days old on July 22, 2026, which is 129 days, the number a pediatric growth chart would use.
Frequently asked questions
How is my exact age calculated?
Calendar-style, the way official age counting works: whole years first (each birthday adds one year), then whole months since the last birthday, then the leftover days. Someone born January 1, 2000 is exactly 26 years, 6 months, and 21 days old on July 22, 2026.
How many days old am I?
Your total days alive is the number of calendar days between your birth date and today, leap days included. A person born January 1, 2000 has been alive 9,699 days as of July 22, 2026. Fun milestones like your 10,000th day are easy to spot from here; just add the difference with the date calculator.
When is my next birthday?
It's the next time your birth month and day come around, counted from today's date. If today is your birthday, the countdown reads zero and the result says so. If you were born on February 29, this calculator counts your birthday as March 1 in non-leap years, so the countdown never skips a year.
Is my birthday sent to a server?
No. All calculations run entirely in your browser, and nothing you type is ever sent to or stored on a server.
How far away was the Moon the night I was born?
Enter your birth date and the page shows the distance from Earth's center to the Moon's center at 9 PM your local time that night. The Moon's orbit is an ellipse, so the distance swings between about 221,500 and 252,700 miles (356,400-406,700 km); the average is about 238,900 miles (384,400 km). On January 1, 2000 at 9 PM Eastern time, for example, it was about 251,000 miles (403,900 km) away, 12,100 miles farther than average.